Posted on 07/07/2006 10:53:34 PM PDT by NormsRevenge
Additional confirmation we are stuck in the Jules Verne/von Braun space exploration paradigms. There's no real break in the cost per pound of human space travel until space-directed nanotechnology becomes viable.
Setting up the shuttle as the standard of reusability is like touting John Kerry as the standard for Vietnam veterans. The shuttle was a failure from the moment the goal changed from its original form to "whatever we can get."
Reusability is supposed to reduce cost, but it doesn't, because the need for multiple stages (the SRBs being the equivalent of a first stage) increases complexity, and the one-size-fits-all STS isn't an appropriate vehicle for every job.
Again, no one (with any connection to reality) is proposing to follow in the shuttle's footsteps. All the things you are listing are problems with the shuttle, not reusability.
Reusability is analogous to the SSTO idea. An SSTO could be built with a sufficient supply of unobtainium.
Even NASA has concluded an SSTO can be built, and yes they stipulate the unobtanium, but that has more to do with a built in excuse for failure than a real need. The one piece of technology actually needed is altitude-compensating nozzles, whether in the form of an aerospike are simply a telescoping bell.
If it could be built, it would still increase the cost per pound to orbit -- and cost reduction (through reusability) is one reason SSTO is touted.
The real point of reusability, SSTO or not, isn't a one off reduction in launch costs. It is the economics of scale. The whole point of reusability is not to reduce the cost with the same number of launches currently consumed. Yet that is precisely the metric that was applied to shuttle development (and subsequently used as an excuse for hamstringing development funds) and it is the metric applied to new launcher development.
The point of reusability is to reduce the marginal cost of launches. First of all, to actually achieve that goal you really do need to craft your requirements around it and not sacrifice that one all important capability for something more sexy. Second, you have to be able to sell the capability that buys you. And when you live in a static world as all politicians and bureaucrats do, well, that is like describing color to a blind man.
Reusability is mythical. New parts are made to replace stuff that is only good for a handful of launches (or one launch).
Name any part where this is true and there is a way to reconfigure the design where you can use a part that is good for hundreds of launches. Engines? There are rocket engines that are good for dozens if not hundreds of restarts and have been run for hours. Thermal protection? The shuttle is the worst case scenario for thermal protection because it uses a lifting reentry with a high sectional density vehicle.
Reprocessing costs for a launch runs to $500 million (a half billion $) and the 30 year old technology is obsolescent. The engines being developed for the new booster will cost less than the liquid fueled SSMEs, will be more powerful, and will not be retrieved from the drink.
Again, you are bringing up the shuttle to discount reusability. The SSME is a ludicrous design for a reusable vehicle. The chamber pressure is incredible, requiring extremely high performance pumps. Extreme performance requires extreme maintenance. The shuttle throws away an expensive external tank. The shuttle started with a reusability requirement then discarded it in all but name in order to get funding.
Don't get me wrong, I am not of the opinion that NASA should take up the task of building a reusable launcher any more than I think Helen Thomas should apply for a job at Hooters.
But I will say that nothing lasting or of any real significance will happen in space until we ditch the whole expendable rocket paradigm and start building real reusable launchers.
But I will say that nothing lasting or of any real significance will happen in space until we ditch the whole expendable rocket paradigm and start building real reusable launchers.For example?
The SSME is a ludicrous design for a reusable vehicle. The chamber pressure is incredible, requiring extremely high performance pumps. Extreme performance requires extreme maintenance.Reusability requires extreme reliability. The engines have been reliable. Extreme performance is what the Shuttle delivered. The SSME isn't a ludicrous design.
All the things you are listing are problems with the shuttle, not reusability.Strange that the USSR didn't learn from the alleged US mistakes and build a vehicle which took off as well as landed like a plane. The most complex machine ever built (in its time at least) wound up being knocked off by the USSR with its Buran system.
Even NASA has concluded an SSTO can be built, and yes they stipulate the unobtanium, but that has more to do with a built in excuse for failure than a real need. The one piece of technology actually needed is altitude-compensating nozzles, whether in the form of an aerospike are simply a telescoping bell.The fact is, that's just wishful thinking. The has been one SSTO, and that is the LEM, which took off from the Moon, not the Earth. That isn't a problem with nozzles, it's a problem of mass budget. The unobtainium referred to above would be the material out of which the single stage would be constructed -- strong enough to hold sufficient fuel to reach orbit, but light enough that most of the mass of the vehicle doesn't have to be dumped, as is the case with every vehicle which has ever reached Earth orbit.
The real point of reusability, SSTO or not, isn't a one off reduction in launch costs. It is the economics of scale. The whole point of reusability is not to reduce the cost with the same number of launches currently consumed... The point of reusability is to reduce the marginal cost of launches.And reusability doesn't do that. Expendibles are cheaper, and will remain so, unless and until an SSTO can be done. But the cost per pound to orbit will also have to improve, or what is the point?
you really do need to craft your requirements around it and not sacrifice that one all important capability for something more sexy.What you're saying is, reusability of the vehicle, and not costs or lift capacity or anything else -- is all important. And that doesn't make sense. Space vehicles need to be built to get specific payloads to orbit (and beyond).
Roadmap To MarsMy blueprint for manned travel to Mars, based on reusable spacecraft that continuously cycle between Earth and Mars in permanent orbits, requires much less energy over the long term. Once in place, a system of cycling spacecraft, with its dependable schedule and low sustaining cost, would open the door for routine travel to Mars and a permanent human presence on the red planet. Its long-term economic advantages make it less susceptible to cancellation by congressional or presidential whim. In effect, this system would go a long way toward politician-proofing the Mars program.
Buzz Aldrin, with David Noland,
illus by Jeremy Cook,
Buzz portrait by Michael Kelley
Popular Mechanics
December 2005
Additional confirmation we are stuck in the Jules Verne/von Braun space exploration paradigms. There's no real break in the cost per pound of human space travel until space-directed nanotechnology becomes viable.Additional confirmation that the society has spent too much time watching the Millennium Falcon take off. :') What is space-directed nanotechnology?
The example is negative: We made great strides going to the moon and haven't been back in thirty years because it was so expensive. Every time there has been an incident in a launch system, we stand down for two years going over it in grueling detail, even when we plan on ditching the thing anyway.
How much clearer can you get that politicians and even NASA regard space as an expensive but ultimately unnecessary stunt?
Reusability requires extreme reliability. The engines have been reliable.
Meaningful reuseability requires more than reliability. It requires low cost maintainability. The reliability of the SSME comes with a huge maintenance cost.
Extreme performance is what the Shuttle delivered. The SSME isn't a ludicrous design.
Bleeding edge performance will always be expensive to operate and maintain. And note that I said the SSME is a ludicrous design for a reusable vehicle.
Strange that the USSR didn't learn from the alleged US mistakes and build a vehicle which took off as well as landed like a plane. The most complex machine ever built (in its time at least) wound up being knocked off by the USSR with its Buran system.
Yes, and they got so much use out of that too, didn't they? I guess you can add that to the Shuttle legacy: It helped win the cold war by becoming the same resource sink for the Soviets it is for us.
That isn't a problem with nozzles, it's a problem of mass budget.
Altitude compensating nozzles are very helpful for SSTO designs. That is the only piece of new technology needed. The mass fraction isn't a matter of unobtanium, even NASA has concluded that SSTO mass fraction is obtainable. And quite a few rocket engineers have been saying it is possible since the 80s and a few were promoting it all the way back to the sixties. Mass fraction isn't a matter of magic technology, it is a matter of exercising engineering discipline. Several vehicles including the Saturn IVB stage have exhibited SSTO-like mass fractions. I may be mistaken, but I believe the Titan II only dropped an engine ring with two engines on the way up.
I will grant you the point that these are a long way from being reusable SSTOs, but materials technology has improved considerably since the sixties. What you're saying is, reusability of the vehicle, and not costs or lift capacity or anything else -- is all important. And that doesn't make sense. Space vehicles need to be built to get specific payloads to orbit (and beyond).
Don't be facetious. Of course payload is important. But your question betrays a misunderstanding of what reusability and/or SSTO is all about. The status quo is so hung up on performance at any cost that ends up being exactly what they pay. It would be far more useful to put 10,000lbs into orbit 100 times than it is to put 40,000lbs into orbit once. It is all about access.
Did you hear Hoagland's description of Von Braun's reaction when the design for the Shuttle came back from Congress?
Why Congress was involved in designing the Shuttle is another question. Hoagland was at a beach party with several high NASA mucky-mucks including Von Braun. Yes, Hoagland used to rub elbows with these.
When Von Braun saw the design, tears came to his eyes and he said, "That will get somebody killed."
Who designed the shuttle?
I don't know how many times I have seen this sort of scenario play out between management and engineering, and it usually winds up spilling blood.
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